Method of and tool for blasting rock



(Modem;

J. L. L. KNOX.

METHOD OF AND TOOL FOR BLASTING ROCKS.

No. 291,606. Patented Jan. 8, 1884.

N PETERS. Phnm-Lilhngrnphar. Wash? glam uc.

UNITED STATES arnsr FFIQEO JOHN L. I]. KNOX, OF ALLEGHENY, PENNSYLYAXIA.

METHOD OF AND TOOL FOR BLASTING ROCK.

SPECIFICATION forming part of Letters Patent No. 291,606, dated January 8, 1884.

Application filed February 10, 1833. (Model i v To to whom it may concern/.-

Be it known that I, J ens L. L. Knox, of Allegheny, county of Allegheny, State of Pennsylvania, have invented certain new and useful Improvements in Methods of and Tools for Blasting Rock, of which the following is a specification.

The objects of my invention are, first, to secure control of and absolute accuracy in the line of fracture of the rock; second, to obtain rectangular blocks of stone with a single blast.

My invention consists, first, in the method hereinafter described, and, second, in the peculiar form of cutting-instrument by which the grooves in the bore are made, all of which will be hereinafter more fully set forth.

Figure 1 represents a cross-section of an ordinary cylindrical bore; Fig. 2, an .end view of the cutting-instrument; Fig. 2", a side elevation of same; Fig. 3, a cross-section of the bore after the cutting-instrument has been once driven through it; Fig. 4, a like view of the bore after the cutting-instrument has been driven through it a second time at right an gles to the first; Fig. 5, a like view of a modified bore adapted for use where soft rock is blasted; Fig. 6, a diagram of the charge; Fig. 6, a eross-seotion of a here with the grooves in improper position.

Similar letters of reference indicate corre sponding parts.

Heretofore in the blasting of rock one of two methods has been pursued: either the blast has been delivered from a cylindrical or from a triangular bore. In the first case there was no possibility of directing the course of the fracture, and, in consequence, the rock was split wherever weakest, and the resultant blocks of stone were of any and every form. In the last case, when the triangular bore was successfully made, (that is, when it was without twist,) the blocks of stone obtained were still necessarily irregular, from the fact that their corners were obtuse angles. By either of these methods it will be apparent a large proportion of the stone was lost in the dressing, since to fit the rock for most economic purposes it is necessary that it should at least approximate a rectangular form.

In the practice of my invention I first drill the ordinary cylindrical here at right angles to the plane of stratification of the rock. I

then insert and drive lengthwise of said bore a cuttirig-instrument of peculiar form, as will be hereinafter described,whereby two angular grooves are formed lengthwise of the bore. These grooves are so situated as that a plane biseeting them will pass through the axis of the bore. If, new, it be desired to split the rock in a right line, that is to say, to have the fractures on either side of the bore in alignment,) the charge is inserted in tlie bore and exploded, whereupon the liberated gases,ac ting upon the sides of the angular grooves in the manner of a wedge, split the rock in the direction of the plane bisecting the two grooves. On the other hand, if the operator desires to blow out a rectangular corner of rock at a single blast, or to break a large rectangular block into four smaller similar blocks, (as where blocks of the form of a rectangular parallelopipedon are required,) the cutting-instrunient is twice driven through the bore, the longest diameter of the instrument at the sec ond driving being placed at right angles to the aforesaid bisecting plane. The bore will then have four longitudinal grooves and (in section) two long diameters, the latter at right angles to each other, and each bisecting the center of the bore. If, now, the charge be inserted and exploded, there will be two lines of fracture, said two lines being at right angles to each other, whereby in the one case a rectangular mass of the outer rock will be separated from the main body, andin the other case thelarge rectangular rock will be split into four small rectangular masses. It will be understood that each of these longitudinal grooves must be equilateral; otherwise the pressure of the gas would be unequally distributed and the lines of fracture made irregular.

I will now proceed to describe the cuttinginstrument by whichthese grooves are formed.

Referring to Fig. 2, which represents the cutting end of the instrument, it will be seen that the face outline of said cutting end is in the form of a hexagon. The sides 0 are parallel,

and in length and distance apart equal to the sides of a square inscribed within the circle of the cylindrical bore. This construction brings each of the corners (Z in contact with the internal surface of the bore, and thus guides the tool and insures the passage of the plane bisecting the grooves through the center or axis IOC ' of any desired shape.

of the bore. It will be seen by Fig. 6 that if said plane did not pass through said axis the sides ofthe groove would not be equal, and the fractures on the opposite sides of the bore would be necessarily not in alignment. The cutting-edges a of the instrument are of equal length, and are so disposed as that a line joining their points I) would pass through a point equidistant from the ends of the sides 0. The angle formed by the said cutting-edges a may be varied to some extent to suit the character of rock quarried. In practice I find that in working hard rock the adjacent edges a are preferably formed at right angles, while in working soft rock the edges are formed at an acute angle in proportion to the softness. This cut'ting-instrument is constructed solid, with a fiat face, and may be made with a stem Above the cutting-face the body of the instrument is beveled off to give clearance to the tool, and thus prevent it from wedging.

' In order to hold the cutting-instrument in position and prevent all deflection the stem of the instrument is rigidly grasped by nippers constructed like a pair of blacksmiths tongs, and accurately fitting said stem.

The operation of the tool is as follows: The cylindrical bore having been completed, the cutting-face of the instrument is placed'in position above the outlet of the bore, with its points I) in line with the desired line of fracture. The tool, while held firmly in place by the nippers, is driven through the bore by means of sledges. The area of rock embraced within the cutting-edges a, being comparatively small, and the cylindrical bore (extending below the cuttingface of the instrument) allowing the escape of the rock as itis broken down by the said cutting-face, it will be seen that at each blow of the sledge upon the head of thetool that portion of the rock directly beneath the angular face of the tool will become disintegrated and drop into the open cylindrical bore. \Vhen said cylindrical bore becomes 4 choked with this dbris, the tool is removed, and water poured into the hole until a pasty mass is formed, when the hole is cleaned with an ordinary swab, and the operation then proceeded with,

The advantages of my invention are, first, the direction of the fracture in the rock may be accurately controlled; second, the fracture on eitherside of the bore is in alignment; third, rectangular blocks may be blownfrom'the rock at will. 4

Having thus described my invention, what I claim is l. The within-described method of blasting rock, whereby the alignment of the fractures upon the opposite sides of the bore is insured, which consists, essentially, in forming longitudinal grooves in the opposite sides of a cylindrical bore, said grooves having equal sides, and so situated as that a plane bisecting two opposite grooves will bisect the axis of the cylindrical bore, substantially as and for the purposes described.

2. The within-described instrument for cutting grooves in cylindrical blasting bores, said instrument having a hexagonal flat cuttingfaee, two sides, 0, parallel and of length and distance apart equal to the sides of a square inscribed within the circle of the cylindrical bore to be operated upon, and cutting-edges a of equal length, and so situated as that a line joining the points 11 will pass through a point equidistant from the ends of the sides 0, substantially as and for the purposes described.

JNO. L. L. KNOX.

Witnesses:

A. G. JOHNSTON, O. S. JoHNsToN. 

